Meeting Abstract

S10-1.4  Monday, Jan. 7  The control of cnidocyte discharge by light PLACHETZKI, D/C; UC Davis plachetzki@ucdavis.edu

Cnidocytes facilitate both sensory and secretory functions among cnidarians and have been heralded as the most complex animal cell type. Cnidocyte discharge is known to integrate both chemical and mechanical cues from the environment, but, despite more than a century of work aimed at understanding the sensory biology of cnidocytes, the specific sensory receptor genes that regulate their function have remained unknown. Here, in studies of the freshwater hydrozoan Hydra magnipapillata, we show that light constitutes another environmental cue that regulates cnidocyte function and that this property is driven by an opsin-mediated phototransduction cascade. We report that several components of the ciliary phototransduction cascade, including opsin, arrestin and cyclic nucleotide-gated (CNG) ion channel are specifically expressed in a previously described sensory-motor neuronal cell type that enervates components of the hydrozoan battery complex, including cnidocytes and ganglion cells. Next, we describe behavioral data from cnidocyte discharge experiments that were conducted under different light conditions. Our results show that a significant attenuation of cnidocyte discharge is induced by bright light, and that this behavior is ablated when experiments are conducted in the presence of a CNG ion channel inhibitor. Our findings suggest a new, likely ancestral, role for phototransduction in the coordination of cnidocyte discharge amongst cnidarian taxa. The implications of these and other recent findings for our understanding of the sensory attributes of the hydrozoan battery complex are discussed.